Don’t activate groups/sub-groups when expanding/collapsing it get’s in the way of assinging entries by dragging. As the group gets activated and the entry disappers as it may not be in it. It’s mostly for collapsing, since:
Scrolling/PageUp/Down the group-interface while dragging would be helpfull as well (PageUp/Down for people with broken mouse-wheels like me, or people with a laptop)
Add the possibility of removing colors from groups & sub-groups so they don’t appear in the colored group-indicator in the entry-table and make it possible to expand said column. Otherwise it easily overflows.